The present invention relates to a saw arrangement and, in particular, to a saw blade having a liquid transport cavity for use with a lubricating guide support assembly.
Saw blades are commonly used to cut raw materials into intermediate or final products, and as the width of the saw blade is decreased, more product can be cut generating higher productivity. As an example, a simple arrangement of circular saw blades mounted on an arbor were once often used to cut pieces of lumber. In such arrangements which were used for cutting Southern Yellow Pine, the typical width of each circular saw blade was approximately 0.180 inches.
An improvement that was made in this simple arrangement is the provision of a guide support assembly comprising two guide supports with opposed bearing surfaces for maintaining proper alignment of each circular saw blade therebetween during cutting, thereby permitting the reduction of the thickness of the saw blade to dimensions that would have otherwise compromised cutting alignment. The guide support assembly is required because the circular saw blades have been reduced to a thickness rendering them incapable of maintaining a generally planar configuration during cutting, thereby making them unsuitable for use without auxiliary side support. Unfortunately, as saw blade thickness decreases more support must be provided by the bearing surface of the guide support against the saw blade which generates greater friction therebetween. This increase in friction can lead to excessive heating of the saw blade which, in turn, can ultimately lead to carbide insert teeth breakage, sawing deviation, guide pad wear, and saw blade damage.
Further improvements to this saw arrangement were made in the late 1980""s. In a first improvement, cooling of the saw blade is accelerated by the provision of circumferential air slots throughout the saw body, of which the saw blade disclosed in Carter Jr. U.S. Pat. No. 4,776,251 is representative. In Carter Jr. a circular saw blade is disclosed having slots cut in the body thereof using a laser. Each slot consists of an arc of a circle concentric with the saw body and parallel to the peripheral edge of the saw body. The radial width of the slot is selected to be between 0.002 and 0.015 inches and remains constant in the circumferential direction of the saw body between opposed circumferential ends of the slot. The common problem of sawdust packing in similar openings formed in a saw body, as disclosed for example in Jansen-Herfeld U.S. Pat. No. 4,574,676 and as expressly discussed by Carter Jr. at cols. 3-4, is avoided in the circular saw blade of Carter Jr. because of the limitation on the radial width of each slot to less than 0.015 inches and because of the disposition of the slots in a circumferential direction with no radial component. Furthermore, unlike the blade disclosed in Jansen-Herfeld, the circular saw blade of Carter Jr. can be used with guide supports without damaging the bearing surfaces thereof due to the narrowness of each slot and its circumferential arrangement. In this arrangement, the plurality of slots provide a radiator cooling effect that accelerates cooling of the saw blade but the slots fail to reduce any friction generated between the saw body and the bearing surface of the guide supports.
In a second, independent improvement to the saw arrangement having guide supports, an actual reduction of the friction between the saw blade and the guide supports is accomplished by the application within each guide support of a lubricating liquid to the saw body. A conventional saw arrangement including a representative illustration of this improvement is disclosed in McGehee U.S. Pat. No. 4,848,200. In this saw arrangement a mixture of oil and water is applied to a saw body of a circular saw blade as it passes by guide supports retaining the saw blade in proper cutting alignment. Typically the liquid is delivered to a recessed opening in each guide support under a pressure of 35 psi and the guide support is maintained immediately adjacent the saw body at a gap of between 0.001 and 0.003 inches, whereby a thin film of liquid is applied to the saw body as it passes thereby. The application of a lubricating liquid reduces frictionxe2x80x94and thus heatxe2x80x94generated between the guide supports and the saw body.
As a result of such improvements in saw arrangements having guide support assemblies, the conventional thickness of a saw blade in a saw arrangement used to cut Southern Yellow Pine has been reduced from 0.180 inches to 0.080 inches. Nevertheless, a need has arisen in recent years to reduce the thickness of a circular saw blade for cutting Southern Yellow Pine still further as demand for greater productivity in lumber mills has arisen. Such attempts at thinner saw blades generally have been unsuccessful due to insufficient cooling and consequent overheating, and better cooling techniques must be developed to advance this sought-after reduction in saw blade thickness.
The present invention exhibits improved cooling of a saw blade retained in proper cutting alignment by lubricating saw guide supports, thereby advancing attempts to reduce saw blade thickness. In particular, the present invention, when used to cut Southern Yellow Pine, has been found (among other advantages): to provide less maintenance than conventional saw blades; to provide less entailed maintenance operations when maintenance is required than that of conventional saw blades; and to provide a longer operating life than conventional.
Briefly described, the present invention relates to a saw arrangement comprising the combination of a saw blade and a lubricating guide support assembly including two guide supports having opposed bearing surfaces for maintaining the saw blade in proper cutting alignment therebetween. The saw blade includes a saw body that defines a cavity therein and a cutting edge disposed along a periphery of the saw body for cutting during movement of the saw blade. Each guide support includes the bearing surface being disposed immediately adjacent the saw body for support of the saw blade during cutting as well as a lubricating system comprising a recessed area extending from the bearing surface and containing liquid exposed to the saw body, whereby the liquid is applied to the saw body as it passes by the recessed area during movement of the saw blade.
In a feature of the present invention, the cavity is arranged on the saw body to pass by the recessed area during movement of the saw blade and is dimensioned to receive liquid therein for transport away from the recessed area to be distributed to the saw body as well as a cutting area of the saw blade. Preferably, the saw blade is circular, and the saw body is planar and includes three cavities disposed relative to one another at 120 degrees about the center of the saw blade. Each cavity is triangular in cross-section and extends from a first planar side of the saw body to a second planar side thereof. Also, each cavity preferably includes only rounded corners, and each cavity preferably has a radial dimension that varies along a circumferential direction of the circular saw blade between opposed circumferential ends of the cavity.
The present invention also relates to a method of using a circular saw blade itself with a lubricating guide support assembly to cut lumber from Southern Yellow Pine. In particular, the circular saw blade includes a planar saw body having an axial thickness of no greater than 0.080 inches and defines a cavity therein having a radial dimension that varies along a circumferential direction of the circular saw blade between opposed circumferential ends of the cavity. The cavity itself preferably includes a radial dimension greater than 0.015 inches sufficient to receive liquid therein when passing by a recessed area of a lubricating guide support.
The present invention further relates to a method for distributing lubricating and cooling liquid to a cutting area of a saw blade used in combination with a lubricating guide support assembly. In particular, the method includes the steps of delivering liquid into a recessed area of the lubricating guide support, filling a cavity of the saw body with the liquid by passing the cavity immediately adjacent the recessed area, and transporting the liquid away from the recessed area by continuing to move the cavity from the recessed area towards the cutting area. The transported liquid passes from the cavity when the cavity moves beyond the bearing surface as a result of air turbulence and inertial forces, and the liquid is consequently distributed both to the saw body of the blade as well as to the cutting area thereof including the carbide insert teeth of the saw blade.